Display device, its manufacturing method, and display medium

ABSTRACT

A display system is built up of at least one display cell comprising an assembly which has at least a first electrode and a second electrode and in which there are mutually non-miscible first and second liquids filled, wherein either one of the first and second electrodes is electrically insulated from the first and second liquids, the first liquid has electrical conductivity or polarity, and voltage is applied to one or both of the first and second electrodes, whereby the first liquid and the second liquid can vary in position to produce a display. Even after an applied voltage is shut off at a position to which the first and second liquids have migrated, the positions of the first and second liquids that have migrated are retained to keep memory capability going on.

ART FIELD

The present invention relates generally to a display system based onelectrophoresis and its manufacture method as well as a display mediumincorporating that display system, and more particularly a displaysystem capable of sustaining a display state even after an appliedvoltage is shut off and its manufacture method as well as a displaymedium.

BACKGROUND ART

In recent years, there has been a display system developed, whichharnesses a phenomenon in which, by applying voltage to anelectrophoresis display device wherein a microcapsule havingelectrophoresis particles and a dispersion medium is interleaved as thatelectrophoresis display device between two electrodes, theelectrophoresis particles migrate through the microcapsule towardelectrodes having different polarities by way of electrophoresis (seeJP-A's 2002-357853 and 2002-333643). That display system is capable ofproducing color displays, because microcapsules containing yellow,magenta and cyan dispersion media, respectively, are used with each onemicrocapsule interleaved between a pair of associated electrodes foreach color.

There has also been a display system developed, in which a plurality ofcells, each having an electrode having a hydrophobic surface inopposition to an electrode having a hydrophilic surface, are filled withwater and colored oil so that at no applied voltage, the colored oilspreads over the hydrophobic electrode surface, and at a voltage appliedbetween the electrodes, the colored oil migrates toward and builds up ona given site of the hydrophobic electrode surface (see InternationalPublication Nos WO 2004/104670, WO 2004/068208 and WO 2004/104671). Thisdisplay system, too, is capable of producing color displays by use ofoils colored in yellow, magenta and cyan.

With the prior art display system set forth in JP-A's 2002-357853 and2002-333643, however, there is a problem that it is difficult to arrangemicrocapsules without giving rise to defects, resulting in an imagequality deterioration.

With the prior art display system set forth in International PublicationNos WO 2004/104670, WO 2004/068208 and WO 2004/104671, a problem is thatwhen the application of voltage is shut off, the oil migrating to andbuilding up on the given site of the hydrophobic electrode comes tospread over the hydrophobic electrode surface; there is lack of anymemory capability. This requires perpetual power supply, leading to afailure in cutting down power consumption.

DISCLOSURE OF THE INVENTION

One object of the present invention is to provide a fast-response,low-consumption display system and manufacture method thereof and adisplay medium.

According to one embodiment of the present invention, that object isachievable by the provision of a display system built up of at least onedisplay cell comprising an assembly which has at least a first electrodeand a second electrode and in which there are mutually non-misciblefirst and second liquids filled, wherein either one of said first andsecond electrodes is electrically insulated from said first and secondliquids, said first liquid has electrical conductivity or polarity, andvoltage is applied to one or both of said first and second electrodes,whereby said first liquid and said second liquid can vary in position toproduce a display, wherein:

even after an applied voltage is shut off at a position to which saidfirst and second liquids have migrated, positions of said first andsecond liquids that have migrated are retained to keep memory capabilitygoing on.

According to another embodiment of the invention, the display systemfurther comprises a liquid retainer means for retaining the positions ofsaid first and second liquids that have migrated, after the appliedvoltage is shut off at the positions of said first and second liquidsthat have migrated.

The embodiment here makes surer the retaining of the first and secondliquids that have migrated.

According to yet another embodiment of the invention, said assemblycomprises a set of substrates, at least one of which is transparent, awall portion for holding said set of substrates in opposition to oneanother in such a way as to define a liquid confining space, a 1^(st)-Aelectrode and a 1^(st)-B electrode that are located on one substratethat faces said liquid confining space in an electrically independentway, an intermediate partition located at a boundary site between said1^(st)-A and 1^(st)-B electrodes, and a second electrode that is locatedon another substrate that faces said liquid confining space, whereinsaid 1^(st)-A and 1^(st)-B electrodes are electrically insulated fromsaid first and second liquids; at a voltage applied to said 1^(st)-Aelectrode and said second electrodes or a voltage applied to said1^(st)-B electrode and said second electrode, said second liquid goesover said intermediate partition in such a way as to be able to migratebetween on said 1^(st)-A electrode and on said 1^(st)-B electrode; andsaid intermediate partition works as said liquid retainer means.

In the embodiment here, the voltage applied to the 1^(st)-A electrodeand the second electrode or the voltage applied to the 1^(st)-Belectrode and the second electrode ensures a fast-response display, andthe intermediate partition that forms the liquid retainer means makessurer the retaining of the first and second liquids that have migrated.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said 1^(st)-A electrode and said 1^(st)-B electrode.

In the embodiment here, the deflection of the second liquid toward thewall of the liquid confining space is held back.

According to a further embodiment of the invention, there is a thin filmprovided on said second electrode that faces said liquid confiningspace, wherein the wettability of said second liquid to said thin filmis smaller than that of said second liquid to said 1^(st)-A electrodeand said 1^(st)-B electrode.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, a lipophilicinsulating film is located over the surfaces of said 1^(st)-A electrodeand said 1^(st)-B electrode coming into contact with said first andsecond liquids.

This embodiment ensures that the wettability of the second liquid to thesurface of the 1^(st)-A or 1^(st)-B electrode is much more improved withimprovements in the thickness uniformity of the second liquid.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said insulating layer.

This embodiment prevents the deflection of the second liquid toward thewall of the liquid confining space.

According to a further embodiment of the invention, there is a thin filmprovided on said second electrode that faces said liquid confiningspace, wherein the wettability of said second liquid to said thin filmis smaller than that of said second liquid to said insulating layer.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, said intermediatepartition has a height enough to ensure that when the applied voltage isshut off, said second liquid resting on said 1^(st)-A electrode or said1^(st)-B electrode does not go over it.

In this embodiment, the intermediate partition makes surer the retainingof the second liquid that has migrated.

According to a further embodiment of the invention, said assemblycomprises a set of substrates, at least one of which is transparent, awall portion for holding said set of substrates in opposition to oneanother in such a way as to define a liquid confining space, a 1^(st)-Aelectrode and a 1^(st)-B electrode that are located on one substratethat faces said liquid confining space in an electrically independentway, an intermediate partition located at a boundary site between said1^(st)-A electrode and said 1^(st)-B electrodes to divide said liquidconfining space in a direction along said substrate surface, and asecond electrode that is located on another substrate that faces saidliquid confining space, wherein said 1^(st)-A electrode and said1^(st)-B electrode are electrically insulated from said first and secondliquids; said intermediate partition has an opening that defines aliquid flow path; at a voltage applied to said 1^(st)-A electrode andsaid second electrode or a voltage applied to said 1^(st)-B electrodeand said second electrode, said second liquid passes through the openingin said intermediate partition in such a way as to be able to migratebetween on said 1^(st)-A electrode and on said 1^(st)-B electrode; andsaid intermediate partition works as said liquid retainer means.

In the embodiment here, the voltage applied to the 1^(st)-A electrodeand the second electrode or the voltage applied to the 1^(st)-Belectrode and the second electrode ensures a fast-response display, andthe intermediate partition having an opening makes surer the retainingof the first and second liquids that have migrated.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said 1^(st)-A electrode and said 1^(st)-B electrode.

In the embodiment here, the deflection of the second liquid toward thewall of the liquid confining space is held back.

According to a further embodiment of the invention, there is a thin filmprovided on the side of said second electrode that faces said liquidconfining space, wherein the wettability of said second liquid to saidthin film is smaller than that of said second liquid to said 1^(st)-Aelectrode and said 1^(st)-B electrode.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, a lipophilicinsulating film is located over the surfaces of said 1^(st)-A electrodeand said 1^(st)-B electrode coming into contact with said first andsecond liquids.

This embodiment of the invention ensures that the wettability of thesecond liquid to the surface of the 1^(st)-A or 1^(st)-B electrode ismuch more improved with improvements in the thickness uniformity of thesecond liquid.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said insulating layer.

This embodiment prevents the deflection of the second liquid toward thewall portion of the liquid confining space.

According to a further embodiment of the invention, there is a thin filmprovided on the side of said second electrode that faces said liquidconfining space, wherein the wettability of said second liquid to saidthin film is smaller than that of said second liquid to said insulatinglayer.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, said second liquidhas a surface tension of 10 to 73 dyne/cm at 20° C. and said opening insaid intermediate partition has a width of 1 to 1,000 μm.

In this embodiment, the intermediate partition makes surer the retainingof the second liquid that has migrated.

According to a further embodiment of the invention, a desired pattern oflight block film is provided on the outside of the transparent substrateon a display viewing side.

This embodiment is capable of producing an on/off display depending onwhether or not the second liquid is positioned on an electrode surfaceat a site with no light block film found.

According to a further embodiment of the invention, said second liquidis colored oil.

This embodiment is capable of displaying information or the like in adesired color.

According to a further embodiment of the invention, there is areflection type display where light reflected from within the displaycell is viewed, and the colored oil that is said second liquid filled ineach display cell is any one of yellow magenta, and cyan.

This embodiment is capable of producing a reflection type full-colordisplay.

According to a further embodiment of the invention, there is atransmission type display where light transmitting through the displaycell is viewed, and said first liquid is colored water while the coloredoil that is said second liquid is light blocking black oil.

This embodiment is capable of producing a colored display in a colortransmitting through the colored water and black.

According to a further embodiment of the invention, the colored waterthat is said first liquid filled in each display cell is any one of red,green, and blue.

This embodiment is capable of producing a transmission type full-colordisplay.

According to a further embodiment of the invention, said 1^(st)-Aelectrode and said 1^(st)-B electrode for each display cell areidentical in configuration and position.

The embodiment here ensures that uniform display performance isachievable throughout the display system.

According to a further embodiment of the invention, said assemblycomprises a set of substrates, at least one of which is transparent, awall portion for holding said set of substrates in opposition to oneanother in such a way as to define a liquid confining spaces a 1^(st)-Aelectrode located on one substrate that faces said liquid confiningspace, a 1^(st)-B electrode located on another substrate that faces saidliquid confining space, and a second electrode located substantiallyparallel with said 1^(st)-A electrode and said 1^(st)-B electrode andadapted to divide said liquid confining space, wherein said secondelectrode has a plurality of through-holes in at least a part, said1^(st)-A electrode and said 1^(st)-B electrode are electricallyinsulated from said first and second liquids; at a voltage applied tosaid 1^(st)-A electrode and said second electrode or a voltage appliedto said 1^(st)-B electrode and said second electrode, said second liquidpasses through the through-holes in said second electrode in such a wayas to be able to migrate between said liquid confining space on said1^(st)-A electrode and said liquid confining space on said 1^(st)-Belectrode; and said second electrode works as said liquid retainermeans.

In this embodiment, the voltage applied to the 1^(st)-A electrode andthe second electrode or the voltage applied to the 1^(st)-B electrodeand the second electrode ensures a fast-response display, and the secondelectrode as a liquid retainer means makes surer the retaining of thefirst and second liquids that have migrated.

According to a further embodiment of the invention, said secondelectrode is an electrically conducting material having a plurality ofthrough-holes.

In the embodiment here, the liquid retainer means provides the secondelectrode as such.

According to a further embodiment of the invention, said secondelectrode is an electrically conductive film formed on the surface of aninsulating material having a plurality of through-holes.

In the embodiment here, the liquid retainer means could be formed of anydesired material.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said 1^(st)-A electrode and said 1^(st)-B electrode.

In embodiment here, the deflection of the second liquid toward the wallof the liquid confining space is held back.

According to a further embodiment of the invention, there is a thin filmprovided on said second electrode, wherein the wettability of saidsecond liquid to said thin film is smaller than that of said secondliquid to said 1^(st)-A electrode and said 1^(st)-B electrode.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, a lipophilicinsulating film is located over the surfaces of said 1^(st)-A electrodeand said 1^(st)-B electrode.

This embodiment of the invention ensures that the wettability of thesecond liquid to the surface of the 1^(st)-A or 1^(st)-B electrode ismuch more improved at both liquid confining spaces divided by the secondelectrode, with improvements in the thickness uniformity of the secondliquid.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said insulating layer.

This embodiment prevents the deflection of the second liquid toward thewall of the liquid confining space.

According to a further embodiment of the invention, there is a thin filmprovided on said second electrode, wherein the wettability of saidsecond liquid to said thin film is smaller than that of said secondliquid to said insulating layer.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, said second liquidhas a surface tension of 10 to 73 dyne/cm at 20° C., and saidthrough-holes in said second electrode have a width of 1 to 1,000 μm.

In this embodiment, the second electrode makes surer the retaining ofthe second liquid that has migrated.

According to a further embodiment of the invention, a desired pattern oflight blocking film is provided on the outside of the transparentsubstrate on a display viewing side.

This embodiment is capable of producing an on/off display depending onwhether or not the second liquid is positioned on an electrode surfaceat a site with no light block film found.

According to a further embodiment of the invention, said second liquidis colored oil.

This embodiment is capable of displaying information or the like in adesired color.

According to a further embodiment of the invention, there is areflection type display where light reflected from within the displaycell is viewed, and the colored oil that is said second liquid filled ineach display cell is any one of yellow, magenta, and cyan.

This embodiment is capable of producing a reflection type full-colordisplay.

According to a further embodiment of the invention, said assemblycomprises a set of substrates, at least one of which is transparent, awall portion for holding said set of substrates in opposition to oneanother in such a way as to define a liquid confining space, a 1^(st)-Aelectrode and a 1^(st)-B electrode that are located on one substratethat faces said liquid confining space in an electrically independentway, an oil repellent layer located at a boundary site between said1^(st)-A electrode and said 1^(st)-B electrode, a lipophilic layerlocated in such a way as to cover said 1^(st)-A electrode and said1^(st)-B electrode at a site with no said oil repellent layer located,and a second electrode that is located on another substrate that facessaid liquid confining space, wherein said 1^(st)-A electrode and said1^(st)-B electrode are electrically insulated from said first and secondliquids; and at a voltage applied to said 1^(st)-A electrode and saidsecond electrode or a voltage applied to said 1^(st)-B electrode andsaid second electrode, said second liquid goes over said oil repellentlayer in such a way as to be able to migrate between on said 1^(st)-Aelectrode and on said 1^(st)-B electrode; and said oil repellent layerworks as said liquid retainer means.

In the embodiment here, the voltage applied to the 1^(st)-A electrodeand the second electrode or the voltage applied to the 1^(st)-Belectrode and the second electrode ensures a fast-response display, andthe oil repellent layer that is the liquid retainer means makes surerthe retaining of the first and second liquids that have migrated.

According to a further embodiment of the invention, said oil repellentlayer and said lipophilic layer are located over said 1^(st)-A electrodeand said 1^(st)-B electrode by way of an insulating layer.

In the embodiment here, the range of selection of materials forming theoil repellent layer and lipophilic layer grows much wider.

According to a further embodiment of the invention, said oil repellentlayer and said lipophilic layer each possess electrical insulation.

In the embodiment here, simple layer construction makes easiermanufacturing.

According to a further embodiment of the invention said oil repellentlayer is configured in such a way as to project toward said liquidconfining space.

In this embodiment, the oil repellent layer makes surer the retaining ofthe second liquid that has migrated.

According to a further embodiment of the invention, the wettability ofsaid first liquid to said wall portion is larger than that of said firstliquid to said oil repellent layer and said lipophilic layer.

In the embodiment here, the deflection of the second liquid toward thewall of the liquid confining space is held back.

According to a further embodiment of the invention, there is a thin filmprovided on said second electrode that faces said liquid confiningspace, wherein the wettability of said second liquid to said thin filmis smaller than that of said second liquid to said oil repellent layerand said lipophilic layer.

This embodiment ensures prevention of adhesion of the second liquid tothe second electrode, and improvements in the wet spreading of the firstliquid.

According to a further embodiment of the invention, a desired pattern oflight block film is provided on the outside of the transparent substrateon a display viewing side.

This embodiment is capable of producing an on/off display depending onwhether or not the second liquid is positioned on an electrode surfaceat a site with no light block film found.

According to a further embodiment of the invention, said second liquidis colored oil.

This embodiment is capable of displaying information or the like in adesired color.

According to a further embodiment of the invention, there is areflection type display where light reflected from within the displaycell is viewed, and the colored oil that is said second liquid filled ineach display cell is any one of yellow, magenta, and cyan.

This embodiment is capable of producing a reflection type full-colordisplay.

According to a further embodiment of the invention, there is atransmission type display where light transmitting through the displaycell is viewed, and said first liquid is colored water while the coloredoil that is said second liquid is a light blocking black oil.

This embodiment is capable of producing a colored display in a colortransmitting through the colored water and black.

According to a further embodiment of the invention, the colored waterthat is said first liquid filled in each display cell is any one of red,green, and blue.

This embodiment is capable of producing a transmission type full-colordisplay.

According to a further embodiment of the invention, said 1^(st)-Aelectrode and said 1^(st)-B electrode for each display cell areidentical in configuration and position.

The embodiment here ensures that uniform display performance isachievable throughout the display system.

According to the present invention detailed above, images are displayedby position changes of the first and second liquids due to an appliedvoltage and there can be memory capability kept going on even after theapplied voltage is shut off; it is possible to achieve a fast-response,low-consumption display system that dispenses with perpetual powersupply.

In the inventive display system manufacture method, the oil repellentresin layer is formed, and that resin layer is subjected to patternexposure to make an exposure site lipophilic, so that the oil repellentlayer and the lipophilic layer are formed.

According to another embodiment of the invention, said oil repellentresin layer is subjected to pattern exposure by way of a photocatalystlayer.

With the photocatalyst used in the embodiment here, the exposure site ismore reliably made lipophilic.

With the above manufacture method of the invention, it is possible tomanufacture a display system having a high-definition display cell.

The display medium of the invention comprises at least one such displaysystem as described above, and includes an input terminal for feedingpower and signals from external equipment to each display cell in thedisplay system, wherein at that input terminal the display medium can beconnected to or disconnected from the external equipment.

The inventive display medium as described above keeps memory capabilitygoing on even after disconnected from the external equipment;information can be carried with the display medium only because of noneed of perpetual power supply.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is illustrative in plan of one embodiment of the display systemaccording to the invention.

FIG. 2 is an enlarged, longitudinally sectioned view as taken on lineI-I of the display system shown in FIG. 1.

FIGS. 3A, 3B 3C and 3D are illustrative of the operation of the displaysystem according to the invention.

FIG. 4 is illustrative in section of another embodiment of the displaysystem according to the invention.

FIG. 5 is illustrative in section of yet another embodiment of thedisplay system according to the invention.

FIG. 6 is illustrative in longitudinal section, as in FIG. 2, of afurther embodiment of the display system according to the invention.

FIGS. 7A, 7B, 7C and 7D are illustrative of the operation of the displaysystem according to the invention.

FIGS. 8A, 8B and 8C are illustrative in perspective of examples of theintermediate partition that forms a part of the display system accordingto the invention.

FIG. 9 is illustrative in longitudinal section as in FIG. 2, of afurther embodiment of the display system according to the invention.

FIGS. 10A, 10B, 10C and 10D are illustrative of the operation of thedisplay system according to the invention.

FIG. 11 is illustrative in section of a further embodiment of thedisplay system according to the invention.

FIGS. 12A and 12B are illustrative of a further embodiment of thedisplay system according to the invention.

FIG. 13 is illustrative in section of a further embodiment of thedisplay system according to the invention.

FIG. 14 is illustrative in longitudinal section, as in FIG. 2 of afurther embodiment of the display system according to the invention.

FIGS. 15A, 15B, 15C and 15D are illustrative of the operation of thedisplay system according to the invention.

FIG. 16 is illustrative in section of a further embodiment of thedisplay system according to the invention.

FIG. 17 is illustrative of one embodiment of the display mediumaccording to the invention.

FIGS. 18A, 18B, 18C and 18D are illustrative of how to manufacture thedisplay system in one example of the invention.

FIGS. 19A and 19B are illustrative of how to manufacture the displaysystem in one example of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention are now explained with reference to theaccompanying drawings.

FIG. 1 is illustrative in plan of one embodiment of the display systemaccording to the invention. As shown in FIG. 1, a display system 1 ofthe invention comprises a plurality of display cells 11 (seven displaycells 11A, 11B, 11C, 11D, 11E, 11F, 11G are depicted in FIG. 1). Eachdisplay cell 11 is built up of an assembly which has at least a firstelectrode and a second electrode, and in which mutually non-misciblefirst and second liquids are filled. Either one of the first and secondelectrodes is electrically insulated from the first and second liquidswith the first liquid having electrical conductivity or polarity. By theapplication of voltage to one or both of the first and secondelectrodes, the first and second liquids are displaced to produce adisplay. Each display cell 11 comprises a pixel segment 12 and a spacesegment 13, wherein the pixel segment 12 is capable of producing anon/off display by displacements of the first and second liquids uponvoltage applied on it, so that the display system 1 can provide adisplay of numeric information of “0” to “9”. In the display system 1 ofthe invention, the pixel segment 12 of each display cell 11 has suchmemory capability as can keep on/off displays going on even after theapplied voltage is shut off.

In FIG. 1, it is noted that the boundary line for each display cell 11is indicated by chain lines and the space segment 13 is indicated byoblique lines.

First Embodiment

FIG. 2 is an enlarged, longitudinally sectioned view of the firstembodiment of the display system according to the invention indicativeof the structure of one display cell in a longitudinal section as takenon line I-I in FIG. 1. As shown in FIG. 2, a display cell 11A is builtup of an assembly 21 in which a first liquid 31 having electricalconductivity or polarity and a second hydrophobic liquid 32 are filled.Note here that display cells other than 11A, too, have a similarstructure as shown in FIG. 2.

The assembly 21 comprises a set of substrates 22 and 23 and a wallportion 28 for supporting them in opposition to one another to define aliquid confining space S. On a side that faces the liquid confiningspace S, one substrate 22 comprises a 1^(st)-A electrode 24 and a1^(st)-B electrode 25 which are located in a mutually electricallyindependent way, and an insulating layer 27 that provides a cover forthem. On that insulating layer 27, there is an intermediate partition 29positioned at a boundary site between the 1^(st)-A electrode 24 and the1^(st)-B electrode 25. Another substrate 23 comprises a second electrode26 on the side that faces the liquid confining space S. The side of theassembly 21 that faces the substrate 23 is a display viewing side, andat least the substrate 23 is transparent. On the outside of thesubstrate 23, there is a light block film 30 located, a site with nolight block film 30 found defining a pixel segment 12 and a site withthe light block film 30 found defining a space segment 13.

In the above display cell 11A, the 1^(st)-A electrode 24 and the1^(st)-B electrode 25 are electrically insulated by the insulating layer27 from the first liquid 31 and the second liquid 32. And then, asvoltage is applied to the 1^(st)-A electrode 24 and the second electrode26, the second liquid 32 goes over the intermediate partition 29,migrating into a liquid confining space S2 on the 1^(st)-B electrode 25,as shown in FIG. 3A. In this state, as the applied voltage is shut off,the intermediate partition 29 works as a liquid retainer means, so thatthe second liquid 32 that has migrated into the liquid confining space Son the 1^(st)-B electrode 25 is retained intact, producing memorycapability (FIG. 3B). As voltage is applied to the 1^(st)-B electrode 25and the second electrode 26, the second liquid 32 goes over theintermediate partition 29, migrating into a liquid confining space S1 onthe 1^(st)-A electrode 24 (FIG. 3C). In this state, as the appliedvoltage is shut off, the intermediate partition 29 works as a liquidretainer means, so that the second liquid 32 that has migrated into theliquid confining space S1 on the 1^(st)-A electrode 24 is retainedintact, producing memory capability (FIG. 3D). Such display cell 11A iscapable of producing on/off displays depending on whether or not thereis the second liquid 32 positioned on the electrode surface (the1^(st)-A electrode 24) of the site with no light block film 30 found(the pixel segment 12).

It is here appreciated that the area and configuration of the 1^(st)-Aelectrode 24 and the 1^(st)-B electrode 25, and the volume andconfiguration of the liquid confining space S1 on the 1^(st)-A electrode24 and the liquid confining space S2 on the 1^(st)-B electrode 25 may ormay not be identical with one another.

The substrate 23 that forms a part of the display cell 11A, because ofbeing positioned on the display viewing side as described above, shouldbe transparent. When the display cell 11A works on a reflection mode, itis not necessary for the opposite substrate 22 to be transparent;however, when the display cell 11A operates on a transmission mode, thatopposite substrate 22 must be transparent. For the substrate 22, 23, forinstance, a transparent substrate such as a glass or transparent resinsubstrate could be used. When it is not necessary for the substrate 22to be transparent, use may be made of a metal substrate, a ceramicsubstrate, an opaque glass substrate that is roughened at a surfacefacing away from an electrode-formation surface or provided with a metalfilm by means of vapor deposition, an opaque resin substrateincorporated with a dye or pigment, etc. The thickness of the substrate22, 23 could be determined while taking what is used for it, etc. intoaccount. For instance, an appropriate selection could be made from therange of 10 μm to 5 mm, and preferably 100 μm to 2 mm.

The 1^(st)-A electrode 24, the 1^(st)-B electrode 25 and the secondelectrode 26 that form a part of the display cell 11A are connected tovoltage application units (not shown), respectively, and operate suchthat electrode charges are optionally controllable in the appliedvoltage range of, for instance, 1 to 100 V. Positioned on the displayviewing side, the second electrode 26 could be provided in the form of atransparent electrode formed of, for instance, indium tin oxide (ITO)zinc oxide (ZnO), and tin oxide (SnO) by means of general film-formationtechniques such as sputtering vacuum vapor deposition, and CVDtechnique. The second electrode 26 could be such that the first liquid31 is at a potential nearly equal to that of the second electrode 26;for instance, it could be formed of not only the planar electrode asdescribed above, but also at least one needle or mesh electrode providedwithin the liquid confining space S as an example. When the display cell11A operates on a transmission mode, the 1^(st)-A electrode 24 and the1^(st)-B electrode 25 should be transparent as is the case with thesecond electrode 26. When the display cell 11A works on a reflectionmode, on the other hand, the 1^(st)-A electrode 24, and the 1^(st)-Belectrode 25 may be a metal electrode such as a Cu, Ag, Au or Al one,not a transparent one.

It is here noted that there could just as easily be a thin film providedon the second electrode 26 that faces the liquid confining space S. Inthis case, the wettability of the second liquid 32 to that thin filmcould be smaller than that of the second liquid 32 to the insulatinglayer 27. This is helpful for prevention of adhesion of the secondliquid 32 to the second electrode 26, and for improvements in the wetspreading of the first liquid 31. Referring to the magnitude of theabove wettability, the contact angle of a droplet of the second liquidis measured with a contact angle meter, and a smaller wettability hereis defined by a larger contact angle.

For the insulating layer 27 that forms a part of the display cell 11A,use could be made of insulating materials such as polyimide resin, SiO₂,SiN₄, acrylic resin, fluororesin, polyamide resin, polyethyleneterephthalate, polypropylene, polystyrene, silicone resin, quartz, epoxyresin, polyethylene, and polytetrafluoro-ethylene with or without tracecurrents passing through them. Among others, it is preferable to use alipophilic insulating material such as polyimide resin, SiO₂, acrylicresin or silicone resin, because of having improved wettablity to thesecond liquid 32, so leading to improvements in the thickness uniformityof the second liquid 32. The term “lipophilic” here is understood tomean that a droplet of tetrachloroethane has a contact angle of up to20°, and preferably up to 10° as measured with a contact angle meter.

It is here appreciated that when the display cell 11A works on atransmission mode, a transparent insulating material is selected fromthe foregoing for the insulating layer 27.

For the wall portion 23 that forms a part of the display cell 11A, usecould be made of resin materials such as ultraviolet curable urethaneacrylate resin, epoxy resin, epoxy acrylate resin, ester acrylate resin,acrylate resin, thermosetting phenol resin, melamine resin, polyesterresin, epoxy resin, polyurethane resin, polyimide resin, and urea resin.The liquid confining space S defined by the cooperation of the wallportion 28 with the opposite substrates 22 and 23 could be set to therange of, for instance, 1 to 1,000 μm.

It is here noted that the wettability of the first liquid 31 to the wallportion 28 could be larger than that of the first liquid 31 to theinsulating layer 27 that provides a cover for the 1^(st)-A electrode 24and the 1^(st)-B electrode 25. By doing so, it is possible to preventthe second liquid 32 from deflecting toward the wall portion 28 of theliquid confining space S.

The intermediate partition 29 that forms a part of the display cell 11Ais a liquid retainer mean, and has a height such that when the appliedvoltage is shut off, the second liquid resting on the 1^(st)-A electrode24 or the 1^(st)-B electrode 25 does not go over it. While theintermediate partition 29 is configured into a rectangular shape insection as typically shown, it is appreciated that it may vary insectional width from site to site, its upper end may be formed of acurved surface rather than a planar surface, its upper end may be of apointed shape, etc. Such intermediate partition 29 could be formed bythe lamination of a photosensitive film at a desired thickness, followedby use of a photolithography technique or a 2P technique (aphoto-polymerization process wherein a liquid ionizing radiation curableresin is coated on the surface of a master plate blank, then configuredby extrusion under pressure, and finally cured by irradiation withionizing radiation), and optionally made up of a material selected fromthe above materials for the wall portion 28.

The first liquid 31 to be filled in the assembly 21 is an electricallyconductive or polar liquid such as water, an alcohol or an acid. On theother hand, the second liquid 32 is a hydrophobic liquid for which usecould be made of oils such as heptane, hexane, nonane, decane, octane,dodecane, tetradecane, octadecane, hexadecane, dodecyldecane, ethyleneglycol monobutyl ether acetate, diethylene glycol monobutyl etheracetate, and ethyl benzoate. Between the specific gravity g1 of thefirst liquid 31 and the specific gravity g2 of the second liquid 32,there should preferably be a relation of g1≦g2.

In the invention, the second liquid 32 could be colored oil wherebyinformation or the like could be displayed in a desired color.

When the display cell 11A operates on a transmission mode, the firstliquid 31 could be a colored liquid while the second liquid 32 is alight blocking black oil, whereby on/off displays could be generated intwo colors, a color transmitting through the colored liquid 31 andblack.

There is no particular limitation on the light block film 30 that formsa part of the display cell 11A; a light blocking resin film and a metalfilm could be used alone or in combination. The light block film 30could also be colored in a desired color.

The display cell 11A is not always limited to the above structure. Thedisplay cell 11A could have a structure wherein its side facing thesubstrate 22 is a viewing side and the light block film 30 is providedon the outside of the substrate 22, as shown typically in FIG. 4. Inthis case, the substrate 22 is transparent, and so are the 1^(st)-Aelectrode 24, the 1^(st)-B electrode 25 and the insulating layer 27.With the display cell 11A working on a transmission mode, the substrate23 and the second electrode 26 are transparent, too. With no light blockfilm 30 provided, displays could be generated by virtue of displacementsof the first and second liquid 31 and 32 due to their movement.

Alternatively, use could be made of a structure wherein the intermediatepartition 29 is directly formed on the substrate 23, as shown in FIG. 5.

The display cell forming the display system of the invention is notalways limited to such structure as to provide displays of numericinformation of “0” to “9” or the like as shown in FIG. 1. For instance,when the display cell operates on a reflection mode, a plurality ofdisplay cells, each using the oil colored in any one of yellow, magentaand cyan as the second liquid, could be arrayed in a matrix or otherform for reflection-mode full-color displays. On the other hand, whenthe display cell works on a transmission mode with a colored liquid asthe first liquid 31 and a light blocking black oil as the second liquid32, a plurality of display cells, each using any one of red, green andblue liquids as the above colored liquid 31, could be arrayed in amatrix or other form for transmission-mode full-color displays.

A plurality of unit cells, each having the 1^(st)-A electrode 24 and the1^(st)-B electrode 25 in the same location and configuration, could bearrayed in a matrix or other form, whereby consistent displayperformance could be achieved throughout the display system even in theabsence of, for instance, the light block film 30.

Second Embodiment

FIG. 6 is illustrative, as in FIG. 2, of the second embodiment of thedisplay system according to the invention, and indicative of thestructure of one display cell. According to the embodiment of FIG. 6, inan assembly 41 of a display cell 11A, there are an electricallyconductive or polar, first liquid 31 and a hydrophobic, second liquid 32filled.

The assembly 41 comprises a set of substrates 42 and 43 and a wallportion 48 for supporting them in opposition to one another to define aliquid confining space S. On a side that faces the liquid confiningspace S, one substrate 42 comprises a 1^(st)-A electrode 44 and a1^(st)-B electrode 45 which are located in a mutually electricallyindependent way, and an insulating layer 47 that provides a cover forthem. On that insulating layer 47, there is an intermediate partition 49positioned at a boundary site between the 1^(st)-A electrode 44 and the1^(st)-B electrode 45 in such a way as to divide the liquid confiningspace S. Another substrate 43 comprises a second electrode 46 on theside that faces the liquid confining space S, and another end of theabove intermediate partition 49 is joined to the substrate 43. The aboveintermediate partition 49 has an opening 49 a that provides a liquidflow path. The side of the assembly 41 that faces the substrate 43 is adisplay viewing side, and at least the substrate 43 is transparent. Onthe outside of the substrate 43, there is a light block film 50 located,a site with no light block film 50 found defining a pixel segment 12 anda site with the light block film 50 found defining a space segment 13.

In the above display cell 11A, the 1^(st)-A electrode 44 and the1^(st)-B electrode 45 are electrically insulated by the insulating layer47 from the first liquid 31 and the second liquid 32. And then, asvoltage is applied to the 1^(st)-B electrode 45 and the second electrode46, the second liquid 32 goes through the opening 49 a in theintermediate partition 49, migrating into a liquid confining space S1 onthe 1^(st)-A electrode 44, as shown in FIG. 7A. In this state, as theapplied voltage is shut off, the intermediate partition 49 works as aliquid retainer means so that the second liquid 32 that has migratedinto the liquid confining space S1 on the 1^(st)-A electrode 44 isretained intact, producing memory capability (FIG. 7B). As voltage isapplied to the 1^(st)-A electrode 44 and the second electrode 46, thesecond liquid 32 goes through the opening 49 a in the partition 49,migrating into a liquid confining space S2 on the 1^(st)-B electrode 45(FIG. 7C). In this state as the applied voltage is shut off, theintermediate partition 49 works as a liquid retainer means, so that thesecond liquid 32 that has migrated into the liquid confining space S2 onthe 1^(st)-B electrode 45 is retained intact producing memory capability(FIG. 7D). Such display cell 11A is capable of producing on/off displaysdepending on whether or not there is the second liquid 32 positioned onthe electrode surface (the 1^(st)-A electrode 44) of the site with nolight block film 50 found (the pixel segment 12).

It is here appreciated that the area and configuration of the 1^(st)-Aelectrode 44 and the 1^(st)-B electrode 45, and the volume andconfiguration of the liquid confining space S1 on the 1^(st)-A electrode44 and the liquid confining space S2 on the 1^(st)-B electrode 45 may beidentical with, or different from, one another.

The intermediate partition 49 that forms a part of the display cell 11Ais the liquid retainer means, and there is no particular limitation onthe opening 49 a that provides a liquid flow path; for instance, thatopening could be such a slit-form opening as depicted in FIG. 8A,multiple such elliptic openings as depicted in FIG. 8B, and multiplesuch oval openings as depicted in FIG. 8C. However, it is desired thatthe width W of the opening 49 a be in the range of 1 to 1,000 μm, andpreferably 1 to 100 μm. As the opening width W is less than 1 μm, thereis an increased resistance with which the second liquid 32 passesthrough the opening 49 a, and at greater than 1,000 μm, the intermediatepartition 40 often loses its own liquid retainer function.

Referring again to FIGS. 8A, 8B and 8C, it is noted that apart from theopening 49 a, the intermediate partition 49 is provided with an opening49 b that makes it easy for the first liquid 31 to go through theintermediate partition 49 in a direction opposite to that of the secondliquid. When such opening 49 b is in contact with the level of thesecond liquid 32 while the intermediate partition 49 functions as theliquid retainer means, it is desired that the opening width W be in therange of 1 to 1,000 μm and preferably 1 to 100 μm, as is the case withthe above opening 49 a. However, there is no limitation on how manyopenings 49 b are used, and what configuration they are used in. Thetotal area of the opening 49 a in the intermediate partition 49 could beoptionally determined while taking the flowability, etc of the secondliquid 31 and the second liquid 32 into account.

The assembly 41 comprising such intermediate partition 49, especiallythe one having such slit-form opening 49 a as depicted in FIG. 8A, couldbe formed by providing the substrates 42 and 43 with partition membersthen forming the opening 49 b through the partition member on the sideof the substrate 43 by means of laser processing, machining or the like,and finally positioning the substrates 42 and 43 in such a way as toarrange the ends of the partition members in opposition to one anothervia a desired gap (the opening 49 a). In the case, the formation of thepartition members to the substrates 42 and 43 could be achieved as isthe case with the above intermediate partition 29. The assembly 41having the intermediate partition 49 configured as in FIG. 3B or 8Ccould be formed by forming the intermediate partition 49 on onesubstrate as is the case with the above intermediate partition 29, thenforming the opening 49 a, 49 b by means of laser processing machining orthe like, and finally engaging the end of the intermediate partition 49with another substrate thereby supporting the substrates 42 and 43 inopposition to one another. The intermediate partition 49 for instancecould be formed of a material selected from the materials for the aboveintermediate partition 29.

The substrates 42, 43 the 1^(st)-A and 1^(st)-B electrodes 44 and 45 andthe second electrode 46 could be similar to the substrates 22, 23 the1^(st)-A and 1^(st)-B electrodes 24 and 25, and the second electrode 26so their explanation is here saved. It is here noted that there couldjust as easily be a thin-film provided on the second electrode 46 thatfaces the liquid confining space S. In this case, the wettability of thesecond liquid 32 to that thin film could be smaller than that of thesecond liquid 32 to the insulating layer 47. This is helpful forprevention of adhesion of the second liquid 32 to the second electrode46 and for improvements in the wet spreading of the first liquid 31.

The insulating layer 47, the wall portion 48 and the light block film50, too, could be similar to the insulating layer 27, the wall portion28 and the light block film 30 in the foregoing embodiment, so theirexplanation is here saved. It is here noted that the wettability of thefirst liquid 31 to the wall portion 48 could be larger than that of thefirst liquid 31 to the insulating layer 47 that provides a cover for the1^(st)-A electrode 44 and the 1^(st)-B electrode 45. By doing so, it ispossible to prevent the second liquid 32 from deflecting toward the wallportion 48 of the liquid confining space S.

The first liquid 31 to be filled in the assembly 41 could be similar tothe first liquid 31 to be filled in the assembly 21 in the foregoingembodiment.

On the other hand, the second liquid 32 to be filled in the assembly 41could be similar to the second liquid 32 to be filled in the assembly 21in the foregoing embodiment, and for that, use could be made of oilssuch as dodecyldecane, methyl glycol acetate, ethyl benzoate, andglycerin acetate, each having a surface tension at 20° C. of 10 to 73dyne/cm, and preferably 15 to 70 dyne/cm. The use of such oil ensuresthat the intermediate partition 49 functions more as a liquid retainermeans.

The “surface tension” here is worked out from a measurement obtained bymeasuring a droplet on a solid with a contact angle meter. It is herepreferable that between the specific gravity g1 of the first liquid 31and the specific gravity g2 of the second liquid 32, there is a relationof g1≦g2.

In the invention, the second liquid 32 could be a colored oil wherebyinformation or the like could be displayed in a desired color.

When the display cell 11A operates on a transmission mode, the firstliquid 31 could be a colored liquid while the second liquid 32 is ablack oil having light block capability, whereby on/off displays couldbe generated in two colors a color transmitting through the coloredliquid 31 and black.

The display cell 11A is not always limited to the above structure. Thedisplay cell 11A could have a structure wherein its side facing thesubstrate 42 is a viewing side and the light block film 50 is providedon the outside of the substrate 42. In this case, the substrate 42 istransparent, and so are the 1^(st)-A electrode 44, the 1^(st)-Belectrode 45 and the insulating layer 47. With the display cell 11Aworking on a transmission mode, the substrate 43 and the secondelectrode 46 are transparent, too. With no light block film 50 provided,displays could be generated by virtue of displacements of the first andsecond liquid 31 and 32 due to their movement. Alternatively, use couldbe made of a structure wherein the intermediate partition 49 is directlyformed on the substrate 43.

The display cell forming the display system of the invention is notalways limited to such structure as to provide displays of numericinformation of “0” to “9” or the like as shown in FIG. 1. For instance,when the display cell operates on a reflection mode, a plurality ofdisplay cells, each using the oil colored in any one of yellow, magentaand cyan as the second liquid, could be arrayed in a matrix or otherform for reflection-mode full-color displays. On the other hand, whenthe display cell works on a transmission mode with a colored liquid asthe first liquid 31 and a light block black oil as the second liquid 32,a plurality of display cells, each using any one of red, green and blueliquids as the above colored liquid 31 could be arrayed in a matrix orother form for transmission-mode full-color displays.

A plurality of unit cells, each having the 1^(st)-A electrode 44 and the1^(st)-B electrode 45 in the same location and configuration, could bearrayed in a matrix or other form, whereby consistent displayperformance could be achieved throughout the display system even in theabsence of, for instance, the light block film 50.

Third Embodiment

FIG. 9 is illustrative, as in FIG. 2, of the third embodiment of thedisplay system according to the invention, and indicative of thestructure of one display cell. According to the embodiment of FIG. 9, inan assembly 61 of a display cell 11A, there are an electricallyconductive or polar, first liquid 31 and a hydrophobic, second liquid 32filled.

The assembly 61 comprises a set of substrates 62 and 63 and a wallportion 68 for supporting them in opposition to one another to define aliquid confining space S. On a side that faces the liquid confiningspace S, one substrate 62 comprises a 1^(st)-A electrode 64, and aninsulating layer 67 that provides a cover for it. Another substrate 63comprises a 1^(st)-B electrode 65 located on a side that faces theliquid confining space S, and an insulating layer 67 that provides acover for it. Further there is a second electrode 66 located, which ispositioned substantially parallel with the 1^(st)-A electrode 64 and the1^(st)-B electrode 65 and located in such a way as to divide the liquidconfining space S. This second electrode 66 has a plurality ofthrough-holes 66 a that provide a liquid flow path, and works also as aliquid retainer means. The side of the assembly 61 that faces thesubstrate 63 is a display viewing side, and at least the substrate 63 istransparent. On the outside of the substrate 63, there is a light blockfilm 70 located, a site with no light block film 70 found defining apixel segment 12 and a site with the light block film 70 found defininga space segment 13. In the embodiment illustrated, the through-holes 66a are indicated by bold lines for convenience.

In the above display cell 11A, the 1^(st)-A electrode 64 and the1^(st)-B electrode 65 are electrically insulated by insulating layers67, 67 from the first liquid 31 and the second liquid 32. And then, asvoltage is applied to the 1^(st)-A electrode 64 and the second electrode66, the second liquid 32 goes through the openings 66 a in the secondelectrode 66, migrating into a liquid confining space S2 on the 1^(st)-Belectrode 65, as shown in FIG. 10A. In this state, as the appliedvoltage is shut off, the second electrode 66 works as a liquid retainermeans, so that the second liquid 32 that has migrated into the liquidconfining space S2 on the 1^(st)-B electrode 65 is retained intact,producing memory capability (FIG. 10B). As voltage is applied to the1^(st)-B electrode 65 and the second electrode 66, the second liquid 32goes through the openings 66 a in the second electrode 66, migratinginto a liquid confining space S1 on the 1^(st)-A electrode 64 (FIG.10C). In this state, as the applied voltage is shut off, the secondelectrode 66 works as a liquid retainer means, so that the second liquid32 that has migrated into the liquid confining space S on the 1^(st)-Aelectrode 64 is retained intact, producing memory capability (FIG. 10D).With display cell 11A, in a state where the second liquid 32 is retainedin the liquid confining space S2 on the 1^(st)-B electrode 65 side (FIG.10B), the color of the second liquid 32 is seen from the pixel segment12, and in a state where the second liquid 32 is retained in the liquidfilling state S1 on the 1^(st)-A electrode 64 side (FIG. 10D), the colorof the first liquid 31 or the color of the second electrode 66 is seen,whereby on/off displays can be viewed.

It is here appreciated that the volume of the liquid confining space S1on the 1^(st)-A electrode 64 side may or may not be identical with thatof the liquid confining space S2 on the 1^(st)-B electrode 65 side.

The substrates 62 and 63 that forms a part of the display cell 11A couldbe similar to the substrates 22 and 23 in the foregoing embodiments, sotheir explanation is saved.

The 1^(st)-A electrode 64 the 1^(st)-B electrode 65 and the secondelectrode 66 that form a part of the display cell 11A are connected tovoltage application units (not shown), respectively, and operate suchthat electrode charges are optionally controllable in the appliedvoltage range of, for instance, 1 to 100 V. Positioned on the displayviewing side, the 1^(st)-B electrode 65 could be provided in the form ofa transparent electrode formed of, for instance, indium tin oxide (ITO),zinc oxide (ZnO), and tin oxide (SnO) by means of general film-formationtechniques such as sputtering, vacuum vapor deposition, and CVDtechnique. Like the 1^(st)-B electrode 65 the st-A electrode 64 and thesecond electrode 66 could be transparent, and formed of an electricallyconductive material such as Cu, Ag, Au or Al.

The second electrode 66 also functions as a liquid retainer means asdescribed above, and each through-hole 66 a should desirously has awidth in the range of 1 to 1,000 μm, and preferably 1 to 100 μm. As thewidth W of the through-holes 66 a is less than 1 μm, there is anincreased resistance with which the second liquid 32 passes through thethrough-holes 66 a, and at greater than 1,000 μm, the second electrode66 often loses its own liquid retainer function. Such second electrode66 could be in a mesh form, and the total area of the through-holes 66 ain the second electrode 66 could be optionally determined while takingthe flowability, etc of the first and second liquids 31 and 32 used intoaccount.

In the invention, as illustrated in FIG. 11, the second electrode 66could just as easily be provided with a plurality of through-holes 66 ain a region corresponding to the space segment 13. This ensures that ina state where, as described above, the second liquid 32 is retained inthe liquid confining space S1 on the 1^(st)-A electrode 64 side (FIG.10D), a flat site of the second electrode 66 (with no through-holesfound) is viewed from the pixel segment 12, resulting in visibilityimprovements.

It is here noted that there could be a thin film provided on the surfaceof the second electrode 66, and the wettability of the second liquid 32to that thin film could be smaller than that of the second liquid 32 tothe insulating layer 67. This is helpful for prevention of adhesion ofthe second liquid 32 to the second electrode 66, and for improvements inthe wet spreading of the first liquid 31.

Although the insulating layers 67, 67 that form a part of the displaycell 11A could be similar to the insulating layers 27 in the precedingembodiments, it is preferable that the insulating layer 67 on thesubstrate 63 side (on the 1^(st)-B electrode 65) is in a transparentinsulating layer form that is made up of a transparent insulatingmaterial selected from the above insulating materials.

The wall portion 68 and the light block film 70 that form a part of thedisplay cell 11A could be similar to the wall portion 28 and the lightblock film 30 in the preceding embodiments, so their explanation issaved. It is appreciated that the wettability of the first liquid 31 tothe wall portion 86 could be larger than that of the first liquid 31 tothe insulating layer 67 that provides a cover for the 1^(st)-A and1^(st)-B electrodes 64 and 65, thereby preventing the deflection of thesecond liquid 32 toward the wall portion 68 of the liquid confiningspace S.

The first liquid 31 to be filled in the assembly 61 could be similar tothe first liquid 31 to be filled in the assembly 21 in the foregoingembodiment.

On the other hand, the second liquid 32 to be filled in the assembly 61could be similar to the second liquid 32 to be filled in the assembly 21in the foregoing embodiment, and for that, use could be made of oilssuch as dodecyldecane, ethylene glycol monobutyl ether acetate,diethylene glycol monobutyl ether acetate, and ethyl benzoate, eachhaving a surface tension at 20° C. of 10 to 73 dyne/cm, and preferably1′ to 70 dyne/cm, thereby ensuring that the second electrode 66functions more as a liquid retainer means. It is here preferable thatbetween the specific gravity g1 of the first liquid 31 and the specificgravity g2 of the second liquid 32, there is a relation of g1≦g2.

In the invention, the second liquid 32 could be colored oil wherebyinformation or the like could be displayed in a desired color.

The display cell 11A is not always limited to the above structure. Forinstance, the second electrode 66 could be provided by forming anelectrically conductive film on an insulating substrate havingthrough-holes 66 a. In this case, the insulating substrate could beformed of insulating materials such as polyimide resin, SiO₂, SiN₄,acrylic resin, fluororesin, polyamide resin, polyethylene terephthalate,polypropylene, polystyrene, silicone resin, quartz, epoxy resin,polyethylene, and polytetrafluoro-ethylene.

The 1^(st)-A electrode 64 and the 1^(st)-B electrode 65 could just aseasily be provided in a desired pattern, rather than all over thesurfaces of the substrates 62 and 63. As shown typically in FIGS. 12A,the 1^(st)-A electrode 64 located on the substrate 62 could be providedin a pattern corresponding to the light block film 70, and the 1^(st)-Belectrode 65 located on the substrate 63 could be provided in a patterncorresponding to a site with no light block film 70 formed. In such anarrangement, as voltage is applied (FIG. 12B) to between the 1^(st)-Aelectrode 64 and the second electrode 66 in a state where there is thesecond liquid 32 in the liquid confining space S1, the second liquid 32goes through the through-holes 66 a in the second electrode 66,migrating more into the region (indicated by broken oblique lines) ofthe pixel segment 12 in the liquid confining space S2. And thereafter,as voltage is applied to the 1^(st)-B electrode 65 and the secondelectrode 66, the second liquid 32 goes through the through-holes 66 ain the second electrode 66, migrating more into the region of the spacesegment in the liquid confining space S1, leading to more effectivemigration of the first liquid 31 and the second liquid 32.

Further the display cell 11A could be configured in such a way as tohave no light block layer 70, as shown in FIG. 13.

Still further, the display cell that forms a part of the display systemof the invention is not always limited to such a structure as shown inFIG. 1, viz., the one capable of producing displays of numericinformation “1” to “9”. For instance, a plurality of display cells, eachusing any one of yellow, magenta and cyan-colored oils as the secondliquid, are arrayed in a matrix or other form for reflection-modefull-color displays.

Fourth Embodiment

FIG. 14 is illustrative, as in FIG. 2 of the fourth embodiment of thedisplay system according to the invention, and indicative of thestructure of one display cell. In the embodiment illustrated in FIG. 14,an electrically conductive or polar, first liquid 31 and a hydrophobic,second liquid 32 filled in an assembly 81 of the a display cell 11A.

The assembly 81 comprises a set of substrates 82 and 83 and a wallportion 88 for supporting them in opposition to one another to define aliquid confining space S. On a side that faces the liquid confiningspace S, one substrate 82 comprises a 1^(st)-A electrode 84 and a1^(st)-B electrode 85 which are located in a mutually electricallyindependent way, and an insulating layer 87 that provides a cover forthem. On that insulating layer 87 there is an oil repellent layer 89Apositioned at a boundary site between the 1^(st)-A electrode 84 and the1^(st)-B electrode 85 and there is a lipophilic layer 89B provided on asite with no oil repellent layer 89A formed. Another substrate 83comprises a second electrode 26. The side of the assembly 81 that facesthe substrate 83 is a display viewing side, and at least the substrate83 is transparent. On the outside of the substrate 83, there is a lightblock film 90 located, a site with no light block film 90 found defininga pixel segment 12 and a site with the light block film 90 founddefining a space segment 13.

In the above display cell 11A, the 1^(st)-A electrode 84 and the1^(st)-B electrode 85 are electrically insulated by the insulating layer87 from the first liquid 31 and the second liquid 32. And then, asvoltage is applied to the 1^(st)-A electrode 84 and the second electrode86, the second liquid 32 goes over the oil repellent layer 89A,migrating onto the 1^(st)-B electrode 85 (the lipophilic layer 89B) asshown in FIG. 15A. In this state, as the applied voltage is shut off theoil repellent layer 89A works as a liquid retainer means, so that thesecond liquid 32 that has migrated onto the 1^(st)-B electrode 85 isretained intact, producing memory capability (FIG. 15B). As voltage isapplied to the 1^(st)-B electrode 85 and the second electrode 86, thesecond liquid 32 goes over the oil repellent layer 89A, migrating ontothe 1^(st)-A electrode 84 (lipophilic layer 89B)(FIG. 15 a). In thisstate, as the applied voltage is shut off, the oil repellent layer 89Aworks as a liquid retainer means, so that the second liquid 32 that hasmigrated onto the st-A electrode 84 is retained intact, producing memorycapability (FIG. 15D). Such display cell 11A is capable of producingon/off displays depending on whether or not there is the second liquid32 positioned on the electrode surface (the 1^(st)-A electrode 84) ofthe site with no light block film 90 found (the pixel segment 12).

Where to locate the oil repellent layer 89A could be optionallydetermined relative to the 1^(st)-A electrode 84 and the 1^(st)-Belectrode 85, and the area and configuration of the lipophilic layer 89Bon the 1^(st)-A electrode 84 and the 1^(st)-B electrode 85 may or maynot be identical with one another.

The oil repellent layer 89A that forms a part of the display cell 11A isa liquid retainer means, and could be formed of an oil repellentmaterial such as fluororesin, and silicone resin. The oil repellentlayer 89A could have a thickness in the range of, for instance, 0.01 to100 μm, and configured in such a way as to project toward the liquidconfining space S, as shown in FIG. 16. The term “oil repellent” heremeans that the contact angle of a droplet of tetrachloroethane is 35° orgreater, as measured with a contact angle meter.

On the other hand, the lipophilic layer 89B could be made up of amaterial obtained by irradiation (pattern exposure) of an oil repellentfluororesin, silicone resin or the like with ultraviolet radiation,hereby cutting a side chain to impart lipophilic nature to it, or alipophilic material such as acrylate resin. With such pattern exposure,it is possible to form the oil repellent layer 89A and the lipophiliclayer 89B in a high-definition pattern. The lipophilic layer 89B couldhave a thickness of, for instance, 0.01 to 100 um. Identical ordifferent materials could be used to build up the lipophilic layer 89Blocated on the 1^(st)-A electrode 84, and the lipophilic layer 89Blocated on the 1^(st)-B electrode 85. For instance, the lipophilicnature of the lipophilic layer 89B positioned on the 1^(st)-A electrode84 could be lower than that of the lipophilic layer 89B positioned onthe 1^(st)-B electrode 85.

The substrates 82, 83, the 1^(st)-A and B electrodes 84, 85 and thesecond electrode 86 that form part of the display cell 11A could besimilar to the substrates 22, 23 the 1^(st)-A and B electrodes 24 and 25and the second electrode 26 in the foregoing embodiment, so theirexplanation is saved. It is here noted that there could be a thin filmprovided on the second electrode 86 that faces the liquid confiningspace S, and the wettability of the second liquid 32 to that thin filmcould be smaller than that of the second liquid 32 to the insulatinglayer 87. This is helpful for prevention of adhesion of the secondliquid 32 to the second electrode 86, and for improvements in the wetspreading of the first liquid 31.

The insulating layer 87, the wall portion 88 and the light block film 90that form a part of the display cell 11A, too, could be similar to theinsulating layer 27, the wall portion 28 and the light block film 30 inthe preceding embodiment, so their explanation is saved. It isappreciated that the wettability of the first liquid 31 to the wallportion 88 could be larger than that of the first liquid 31 to the oilrepellent and lipophilic layers 89A and 89B, thereby preventing thedeflection of the second liquid 32 toward the wall portion 88 of theliquid confining space S.

The first liquid 31 to be filled in the assembly 81 could be similar tothe first liquid 31 to be filled in the assembly 21 in the foregoingembodiment.

On the other hand, the second liquid 32 to be filled in the assembly 81could be similar to the second liquid 32 to be filled in the assembly 21in the foregoing embodiment, and for that, use could be made of oilssuch as heptane, hexane, nonane, decane, octane, dodecane, tetradecane,octadecane, hexadecane, dodecyldecane, ethylene glycol monobutyl etheracetate, diethylene glycol monobutyl ether acetate, and ethyl benzoate,each having a surface tension at 20° C. of 10 to 73 dyne/cm, andpreferably 15 to 70 dyne/cm, thereby ensuring that the oil repellentlayer 89A functions more as a liquid retainer means. It is herepreferable that between the specific gravity g1 of the first liquid 31and the specific gravity g2 of the second liquid 32, there is a relationof g1≦g2.

In the invention, the second liquid 32 could be a colored oil wherebyinformation or the like could be displayed in a desired color.

When the display cell 11A operates on a transmission mode, the firstliquid 31 could be a colored liquid while the second liquid 32 is ablack oil having light block capability, whereby on/off displays couldbe generated in two colors, a color transmitting through the coloredliquid 31 and black.

The display cell 11A is not always limited to the above structure. Thedisplay cell 11A could have a structure wherein its side facing thesubstrate 82 is a viewing side and the light block film 90 is providedon the outside of the substrate 82. In this case, the substrate 82 istransparent, and so are the 1^(st)-A electrode 84, the 1^(st)-Belectrode 85 and the insulating layer 87 plus the lipophilic layer 89B.With the display cell 11A working on a transmission mode, the substrate83 and the second electrode 86 are transparent, too.

With no light block film 90 provided, displays could be generated byvirtue of displacements of the first and second liquid 31 and 32 due totheir movement.

Alternatively, use could be made of a structure wherein the oilrepellent and lipophilic layers 89A and 89B are directly formed on thesubstrate 83 and the 1^(st)-A and B layers 84 and 85 without theinsulating layer 87, in which case insulating ones are used as the oilrepellent and lipophilic layers 89A and 89B.

The display cell forming the display system of the invention is notalways limited to such structure as to provide displays of numericinformation of “0” to “9” or the like as shown in FIG. 1. For instance,when the display cell operates on a reflection mode, a plurality ofdisplay cells, each using the oil colored in any one of yellow, magentaand cyan as the second liquid, could be arrayed in a matrix or otherform for reflection-mode full-color displays. On the other hand, whenthe display cell works on a transmission mode with a colored liquid asthe first liquid 31 and a light block black oil as the second liquid 32,a plurality of display cells, each using any one of red, green and blueliquids as the above colored liquid 31, could be arrayed in a matrix orother form for transmission-mode full-color displays.

A plurality of unit cells, each having the 1^(st)-A electrode 84 and the1^(st)-B electrode 85 in the same location and configuration, could bearrayed in a matrix or other form, whereby consistent displayperformance could be achieved throughout the display system even in theabsence of, for instance, the light block film 90.

The display medium of the invention comprises one or more such displaysystems as described above, and has an input terminal adapted to feedpower and signals from external equipment to each display cell in thedisplay system at which input terminal the display medium can beconnected to or disconnected from the external equipment.

This ensures that even after there is the display medium removed fromthe external equipment, it is possible to retain memory capabilityenough to carry information with the display medium alone.

FIG. 17 is illustrative of one example of the display medium accordingto the invention. In FIG. 17, the inventive display medium 100 is builtup of a display unit 101 comprising a set of multiple display systemsaccording to the invention and an input terminal 102. There is nolimitation on the number of display systems that build up the displayunit 101 in the display medium 100, and as long as there is the inputterminal 102 somewhere around the display unit 101 (a hatched site inFIG. 17), there is no limitation on where to locate it. The inputterminal 102 is provided to feed power and signals from externalequipment 110 to each display cell in the display system, and aconnector 112 of transmission means 111 linked to the external equipment110 is connected to it. At that input terminal 102, the display medium100 is connectable to or detachable from the external equipment 110.Thus, the desired information can be displayed on the display medium 100upon receipt of power and signals from the external equipment 110 by wayof the input terminal 102 and thereafter, if the connector 112 isremoved out of the input terminal 102 for disconnection of the displaymedium 100 from the external equipment 110, then the display medium 100can be carried at one's disposal.

The external equipment 110, for instance, includes computer means suchas a personal computer and a mainframe computer, telefacsimile machines,copiers, data communications systems and processors for wirelesscommunications, etc., network terminals, and the internet terminals.

Not exclusively, the transmission means 111 could be those capable offeeding power and signals, for instance, electric conductor cables, andhardwire links.

The above embodiments of the invention are provided for the purpose ofillustration alone.

The present invention is now explained in further details with respectto more specific examples.

EXAMPLE 1

First, on a 200 μm thick PET film, a rectangular area (of 20 m×10 mmsize) was set for building up a display system comprising seven displaycells, as shown in FIG. 18A, and sub-areas were set for the sevendisplay cells. A pixel segment of each display cell was set to a 6mm×1.5 mm rectangle (a hatched site in FIG. 18A).

Further, an area for the formation of the 1^(st)-A electrode (a hatchedsite in FIG. 18B) was set in such a way as to include the above pixelsegment, and an area (a hatched site in FIG. 18C) for the formation ofthe 1^(st)-B electrode was set.

Then, a Cr film (of 1,500 Å in thickness) was formed on the PET film bymeans of vapor deposition, and a photosensitive resist (MicroPosit madeby Sipray Co., Ltd.) was applied on that Cr film to form a resist filmby means of photo-lithography. Then, using that resist film as a mask,the Cr film was etched (with an etching solution: a mixed solution ofsulfuric acid and hydrogen peroxide) to form the 1^(st)-A electrode andthe 1^(st)-B electrode for each display cell. Note here that wirings(not shown in FIG. 18) for the connection of the 1^(st)-A and 1^(st)-Belectrodes to an external voltage application unit, too, weresimultaneously formed.

Then, an insulative resin (SE-7492 made by Nissan Chemical Industries,Ltd.) was coated on the PET film by means of bar coating in such a wayas to cover the 1^(st)-A and 1^(st)-B electrodes, and cured to form a0.8 thick insulating layer. This insulating layer was found to have alipophilic property of about 15 in terms of the contact angle of atetrachloroethane droplet.

Then, the 2P technique was used with an acrylic resin having thefollowing composition to form an intermediate partition (of 100 μm inwidth and 150 μm in height) in such a form as indicated by bold lines inFIG. 18D).

Acrylic Resin Composition Urethane acrylate 35 parts by weight (GohselacUV7500B made by Nippon Gosei Co., Ltd.) Acrylate monomer 43 parts byweight (1,6-Hexanediol diacrylate made by Toa Gosei Co., Ltd.) Vinylmonomer 17 parts by weight (Vinylpyrrolidone made by Toa Gosei Co.,Ltd.) Photopolymerization initiator 4 parts by weight(1-Hydroxycyclohexyl phenyl ketone made by Ciba Geigy) Additive 0.5 partby weight (TSF4440 made by GE Toshiba Silicone Co., Ltd.)

Then, a bead-containing ultraviolet curable type resin (LCB-610 made byE.H.C) was used to form a 1 μm wide, 200 um high wall portion on theboundary lines between the display cells and on the outer periphery edgeof the display system-formation rectangular area.

On another PET film of 200 μm in thickness, on the other hand, a displaysystem-formation rectangular area and a pixel segment of each displaycell were set, as described just above. On one surface of the PET film,an indium tin oxide (ITO) film was formed by means of vapor depositionin such a way as to be in alignment with the display system-formationrectangular area to form a second electrode (common electrode). Notehere that wirings for the connection of the second electrode to anexternal voltage application unit, too, were simultaneously formed,although not shown.

Then, on another surface of that PET film, a light blocking resinmaterial having the following composition was applied by screen printingto form a light block film (5 μm in thickness). This light block filmwas provided such that it was opposed to the second electrode by way ofthe PET film and seven pixel segments were bared out.

Light Blocking Resin Composition Black pigment 14 parts by weight (TMBlack #9550 made by Dainichi Seika Kogyo Co., Ltd.) Dispersant 1.2 partsby weight (Dispersbyk111 made by Bic-Chemie) Polymer 2.8 parts by weight(VR60 made by Showa Polymer Co., Ltd.) Monomer 3.5 parts by weight(SR399 made by Sahtomer Co., Ltd.) Initiator 1.6 parts by weight(2-Bynzyl-2-dimethylamino-1-(4- morpholinophenyl)-butane-1 Initiator 0.3part by weight (4,4′-Diethylaminobenzophenone) Initiator 0.1 part byweight (2,4-Diethylthioxanthone) Solvent 75.8 parts by weight (Ethyleneglycol monobutyl ether)

Then, the surface of the PET film having the second electrode on it wasengaged with and compressed against the wall portion of the PET filmhaving the above intermediate partition, etc. on it, after which thewall portion was irradiated with ultraviolet radiation (60 mW/cm², fiveminutes) for curing. For that compression, first, water and oil(dodecyldecane dyed with a blue dye (Oil Blue 5502 made by ArimotoChemical Industries, Ltd.)) were filled at a volumetric ratio of 2:1 ineach display cell on the PET film having the intermediate partition,etc. on it, followed by alignment of the display cells on the two PETfilms.

In this way such an inventive display system as shown in FIG. 2 wasmanufactured.

As a dc voltage of 10 V was applied between all the 1^(st)-A electrodesand the second electrode (common electrode) in all the display cells ofthe manufactured display system, it caused the oil (coloreddodecyldecane) to go over the intermediate partition, migrating into thespace (space segment) on the 1^(st)-B electrodes. As a result,extraneous light was reflected at the 1^(st)-A electrode-formation Crfilm at all the seven pixel segments, so that a figure “8” could beviewed from the side of the PET film having the light block film on it.As the applied voltage was shut off in this state, the same displaystate could be retained for 10 days or longer, indicating that there wasan excellent memory capability achieved.

As a do voltage of 10 V was applied between all the 1^(st)-B electrodeand the second electrode (common electrode), it caused the oil (coloreddodecyldecane) to go over the intermediate partition migrating into thespaces (pixel segments) on the 1^(st)-A electrodes, so that the blue ofthe oil (colored dodecyldecane) could be viewed and the figure “8” couldbe displayed. As the applied voltage was shut off in this state, thesame display state could be retained for 10 days, indicating that therewas an excellent memory capability achieved.

By the optional determination of the 1^(st)-A or the 1^(st)-B electrodesto which direct-current voltage was applied at the second electrode(common electrode), any desired figure of “0” to “9” could be displayedby reflected light or the blue of the oil (colored dodecyl-decane). Inthis case, too, there was an excellent memory capability achieved.

EXAMPLE 2

As in Example 1, the 1^(st)-A and 1^(st)-B electrodes were formed on a200 μm thick PET film for each display cell, and an insulating layer wasprovided in such a way as to cover the 1^(st)-A and 1^(st)-B electrodes.

On the other hand, the second electrode (common electrode) was formed onanother PET film of 200 μm in thickness as in Example 1, and a lightblock film was formed on another surface of that PET film as in Example1.

Then, the 2P technique was used with an acrylic resin having a similarcomposition as in Example 1 to form an intermediate partition (of 100 μmin width and 100 μm in height) on the insulating layer on the PET filmhaving the above 1^(st)-A and 1^(st)-B electrodes, and on the secondelectrode on the PET film with that second electrode. The intermediatepartitions were formed at the position indicated by a bold line in FIG.18D and the intermediate partition patterns formed on both the PET filmswere symmetric with respect to plane. Each intermediate partition had inits upper end side 30 semicircular cutouts of 10 μm in radius at a 0.2mm pitch. Then, 30 circular openings of 10 μm in radius were arrayed ata 0.2 mm pitch at a position 50 μm away from the upper end side of theintermediate partition formed on the PET film having the secondelectrode toward the PET film side by means of laser irradiation.

Then, a bead-containing ultraviolet curable type resin (LCB-610 made byE.H.C.) was used to form a 1 mm wide, 200 μm high wall portion on theboundary lines between the display cells, each having the 1^(st)-A and 1^(st)-B electrodes and on the outer periphery edge of the displaysystem-formation rectangular area.

Then water and oil (dodecyldecane dyed with a blue dye (Oil Blue 5502made by Arimoto Chemical Industries, Ltd.)) were filled at a volumetricratio of 2:1 in each display cell on the PET film having the wallportion formed, after which another PET film was engaged with andcompressed against that wall portion. In this compressed state, theupper end sides of the intermediate partitions formed on the PET filmswere engaged together to form an intermediate partition for halving theliquid confining space in each cell, the semicircular cutouts wereopposed to one another to from a circular opening. In this state, thewall portion was irradiated with ultraviolet radiation (60 mW/cm², 5minutes) for curing.

In this way, there was such an inventive display system as shown in FIG.6 manufactured, which had such an intermediate partition as shown inFIG. 8C.

As in Example 1, the display performance of the manufactured displaysystem was estimated while the 1^(st)-A and 1^(st)-B electrodes to whichdirect-current voltage was applied at the second electrode (commonelectrode) were optionally selected. As a consequence, any desiredfigure of “0” to “9” could be displayed by reflected light or the blueof the oil (colored dodecyldecane). Even after the applied voltage wasshut off, the same display state could be retained for 10 days orlonger, indicating that there was an excellent memory capabilityachieved.

EXAMPLE 3

As in Example 1, the 1^(st)-A and 1^(st)-B electrodes were formed on a200 μm thick PET film for each display cell, and an insulating layer wasprovided in such a way as to cover the 1^(st)-A and 1^(st)-B electrodes.

On the other hand, the second electrode (common electrode) was formed onanother PET film of 200 μm in thickness as in Example 1, and a lightblock film was formed on another surface of that PET film as in Example1.

Then, the 2P technique was used with an acrylic resin having a similarcomposition as in Example 1 to form an intermediate partition (of 100 μmin width and 80 um in height) on the insulating layer on the PET filmhaving the above 1^(st)-A and 1^(st)-B electrodes, and on the secondelectrode on the PET film with that second electrode. The intermediatepartitions were formed at the position indicated by a bold line in FIG.18D, and the intermediate partition patterns formed on both the PETfilms were symmetric with respect to plane. Then, 30 circular openingsof 10 μm in radius were arrayed at a 0.2 μm pitch at a position 40 μmaway from the upper end side of the intermediate partition formed on thePET film having the second electrode toward the PET film side by meansof laser irradiation.

Then, a bead-containing ultraviolet curable type resin (LCB-610 made byE.H.C.) was used to form a 1 mm wide, 200 μm high wall portion on theboundary lines between the display cells, each having the 1^(st)-A and1^(st)-B electrodes and on the outer periphery edge of the displaysystem-formation rectangular area.

Then, water and oil (dodecyldecane dyed with a blue dye (Oil Blue 5502made by Arimoto Chemical Industries, Ltd)) were filled at a volumetricratio of 2:1 in each display cell on the PET film having the wallportion formed, after which another PET film was engaged with andcompressed against that wall portion. In this compressed state, theupper end sides of the intermediate partitions formed on the PET filmswere opposed to one another at a gap of 40 μm, whereby the liquidconfining space in each cell was halved by the intermediate partitionhaving a slit-form opening of 40 μm in width. In this state, the wallportion was irradiated with ultraviolet radiation (60 mW/cm² 5 minutes)for curing.

In this way, there was such an inventive display system as shown in FIG.6 manufactured, which had such an intermediate partition as shown inFIG. 8A.

As in Example 1, the display performance of the manufactured displaysystem was estimated while the 1^(st)-A and 1^(st)-B electrodes to whichdirect-current voltage was applied at the second electrode (commonelectrode) were optionally selected. As a consequence, any desiredfigure of “0” to “9” could be displayed by reflected light or the blueof the oil (colored dodecyldecane). Even after the applied voltage wasshut off, the same display state could be retained for 10 days orlonger, indicating that there was an excellent memory capabilityachieved.

EXAMPLE 4

First, on a 200 μm thick PET film, a rectangular area (of 20 mm×10 mmsize) was set for building up a display system comprising seven displaycells, as shown in FIG. 19A, and sub-areas were set for the sevendisplay cells. A pixel segment of each display cell was set to a 6mm×1.5 mm rectangle (a hatched site in FIG. 19A).

Further, an area for the formation of the 1^(st)-A and 1^(st)-Belectrodes (a hatched site in FIG. 19B) was set in such a way as toinclude the above pixel segment.

Then, a Cr film (of 1,500 Å in thickness) was formed on the PET film bymeans of vapor deposition, and a photosensitive resist (MicroPosit madeby Sipray Co., Ltd.) was applied on that Cr film to form a resist filmby means of photo-lithography. Then, using that resist film as a mask,the Cr film was etched (with an etching solution: a mixed solution ofsulfuric acid and hydrogen peroxide) to form the 1^(st)-A electrode foreach display cell. Note here that wirings (not shown in FIG. 19) for theconnection of the 1^(st)-A electrode of each display cell to an externalvoltage application unit), too, were simultaneously formed.

In the same way, the 1^(st)-B electrode was formed on another PET filmfor each display cell. Then, on another surface of that PET film, alight blocking resin material as in Example 1 was applied by screenprinting to form a light block film (5 μm in thickness). This lightblock film was provided such that it was opposed to the 1^(st)-Belectrode by way of the PET film and seven pixel segments were baredout.

Then, a 3.8 μm thick insulating layer was provided in such a way as tocover the 1^(st)-A and 1^(st)-B electrodes on the PET film, as inExample 1.

On the other hand photolithography was used with a 0.2 μm thick copperfoil to apply a photosensitive resist (MicroPosit made by Sipray Co.,Ltd.) on it to form a resist film. Then, using that resist film as amask, the copper foil was etched (with an etching solution: a mixedsolution of sulfuric acid and hydrogen peroxide) to form the secondelectrode over a rectangular area of 20 mm×10 my corresponding to theabove display system-formation rectangular area. The second electrodehad 10 μm×10 μm square through-holes at a pitch of 250 μm. Note herethat wirings for the connection of the second electrode to an externalvoltage application unit), too, were simultaneously formed.

Then, a 1 μm wide, 100 μm high wall portion was formed on the boundaryline of each display cell on the PET film having the 1^(st)-A electrode,and on the outer periphery edge of the display system-formationrectangular area.

Then, the second electrode was place across that wall portion, afterwhich, in a state when the second electrode was held on the above wallportion, a 1 mm wide, 100 μm high wall portion was formed as describedabove.

Then, water and oil (dodecyldecane dyed with a blue dye (Oil Blue 5502made by Arimoto Chemical Industries, Ltd.)) were filled at a volumetricratio of 2:1 in each display cell on the PET film having the 1^(st)-Belectrode on it, after with the PET film having the wall portion wasengaged with and compressed against that wall portion. In the compressedstate, the 1^(st)-A and 1^(st)-B electrodes were opposed to one anotherby way of the second electrode in each display cell. And then, in thisstate, the wall portion was irradiated with ultraviolet radiation (60mW/cm², 5 minutes) for curing.

In this way such an inventive display system as shown in FIG. 9 wasmanufactured.

As a dc voltage of 10 V was applied between all the 1^(st)-A electrodesand the second electrode (common electrode) in all the display cells ofthe manufactured display system, it caused the oil (coloreddodecyldecane) to go through the through-holes in the second electrode,migrating into the space on the 1^(st)-B electrode side. Consequently,at all the seven pixel segments, the blue of the oil (coloreddodecyldecane) was viewed from the side of the PET film having the lightblock film formed on it, so that a figure “8” could be displayed. As theapplied voltage was shut off in this state, the same display state couldbe retained for 10 days or longer, indicating that there was anexcellent memory capability achieved.

As a dc voltage of 10 V was applied between all the 1^(st)-B electrodeand the second electrode (common electrode), it caused the oil (coloreddodecyldecane) to go through the through-holes in the second electrode,migrating into the spaces on the 1^(st)-A electrodes, so that extraneouslight was reflected at the copper foil forming a part of the secondelectrode to display a figure “8”. As the applied voltage was shut offin this state, the same display state could be retained for 10 days,indicating that there was an excellent memory capability achieved.

By the optional determination of the 1^(st)-A or the 1^(st)-B electrodesto which direct-current voltage was applied at the second electrode(common electrode), any desired figure of “0” to “9” could be displayedby reflected light or the blue of the oil (colored dodecyl-decane). Inthis case, too, there was an excellent memory capability achieved.

EXAMPLE 5

As in Example 1, the 1^(st)-A and 1^(st)-B electrodes were formed on a200 μm thick PET film for each display cell, and an insulating layer wasprovided in such a way as to cover the 1^(st)-A and 1^(st)-B electrodes.

Then, a 1% by weight isopropyl alcohol solution of an oil repellentfluoroalkylsilane (a 15 mixture (by weight) of TSL8233 and YSL8114 madeby GE Toshiba Silicone Co., Ltd.) was coated by spin coating in such away as to cover the above insulating layer. Thereafter, a mask having alight-transmitting portion was provided over a site corresponding to the1^(st)-A and 1^(st)-B electrodes, and a photo-catalyst composition (abinder resin (TSL8223 made by Toshiba Silicone Co., Ltd.) with aphoto-catalyst titanium oxide contained therein in an amount of 30% byweight) was spin coated on one side of that mask, and dried to form acatalyst layer of 0.1 μm in thickness.

While the above mask was opposed on its catalyst layer side to thesurface coated with the oil repellent fluoroalkylsilane, proximityexposure was carried out (using light having a wavelength of shorterthan 380 nm (254 nm)). Consequently, in each display cell area, an oilrepellent layer (of 0.02 μm in thickness) was formed at a site with no1^(st)-A and 1^(st)-B electrodes found (a non-exposure site) and, in asite corresponding to the 1^(st)-A and 1^(st)-B electrodes, the sidechain of the oil repellent layer was replaced by a hydroxyl group toform a lipophilic layer (of 0.02 μm in thickness).

On the other hand, the second electrode (common electrode) was formed onanother PET film of 200 μm in thickness as in Example 1, and a lightblock layer was formed on another surface of that PET film as in Example1.

Then, a 1 μm wide, 200 μm high wall portion was formed on the boundaryline of each display cell on the PET film having the 1^(st)-B electrode,and on the outer periphery edge of the display system-formationrectangular area, as in Example 1.

Then, water and oil (dodecyldecane dyed with a blue dye (Oil Blue 5502made by Arimoto Chemical Industries, Ltd.)) were filled at a volumetricratio of 2:1 in each display cell on the PET film having the secondelectrode on it, after with the PET film having the wall portion wasengaged with and compressed against that wall portion. And then, thewall portion was irradiated with ultraviolet radiation (60 mW/cm², 5minutes) for curing.

In this way such an inventive display system as shown in FIG. 14 wasmanufactured.

As a dc voltage of 10 V was applied between all the 1^(st)-A electrodesand the second electrode (common electrode) in all the display cells ofthe manufactured display system, it caused the oil (coloreddodecyldecane) to go over the oil repellent layer, migrating into thespace (space segment) on the 1^(st)-B electrode. Consequently, at allthe seven pixel segments, extraneous light was reflected by the Cr filmforming the 1^(st)-A electrode to display a figure “8”. As the appliedvoltage was shut off in this state, the same display state could beretained for 10 days or longer, indicating that there was an excellentmemory capability achieved.

As a dc voltage of 10 V was applied between all the 1^(st)-B electrodeand the second electrode (common electrode), it caused the oil (coloreddodecyldecane) to go over the oil repellent layer, migrating into thespaces (pixel segments) on the 1^(st)-A electrode, so that at the pixelsegments the blue of the oil (colored dodecyldecan) was viewed todisplay a figure “8”. As the applied voltage was shut off in this state,the same display state could be retained for 10 days, indicating thatthere was an excellent memory capability achieved.

By the optional determination of the 1^(st)-A or the 1^(st)-B electrodesto which direct-current voltage was applied at the second electrode(common electrode) any desired figure of “0” to “9” could be displayedby reflected light or the blue of the oil (colored dodecyl-decane). Inthis case, too, there was an excellent memory capability achieved.

POSSIBLE UTILIZATION IN THE INDUSTRY

The present invention is applicable to fields for which memorycapability is needed.

1. A display system built up of at least one display cell comprising anassembly which has at least a first electrode and a second electrode andin which there are mutually non-miscible first and second liquidsfilled, wherein either one of said first and second electrodes iselectrically insulated from said first and second liquids, said firstliquid has electrical conductivity or polarity, and voltage is appliedto one or both of said first and second electrodes, whereby said firstliquid and said second liquid vary in position to produce a display,characterized in that: even after an applied voltage is shut off at aposition to which said first and second liquids have migrated, positionsof said first and second liquids that have migrated are retained to keepmemory capability going on.
 2. The display system of claim 1, whichfurther comprises a liquid retainer means for retaining the positions ofsaid first and second liquids that have migrated, after the appliedvoltage is shut off at the positions of said first and second liquidsthat have migrated.
 3. The display system of claim 2, characterized inthat said assembly comprises a set of substrates, at least one of whichis transparent, a wall portion for holding said set of substrates inopposition to one another in such a way as to define a liquid confiningspace, a 1^(st)-A electrode and a 1^(st)-B electrode that are located ona side of one substrate that faces said liquid confining space in anelectrically independent way, an intermediate partition located at aboundary site between said 1^(st)-A and 1^(st)-B electrodes, and asecond electrode that is located on another substrate that faces saidliquid confining spaces wherein said 1^(st)-A and 1^(st)-B electrodesare electrically insulated from said first and second liquids; at avoltage applied to said 1^(st)-A electrode and said second electrodes ora voltage applied to said 1^(st)-B electrode and said second electrode,said second liquid goes over said intermediate partition in such a wayas to be able to migrate between on said 1^(st)-A electrode and on said1^(st)-B electrode; and said intermediate partition works as said liquidretainer means.
 4. The display system of claim 3, wherein a wettabilityof said first liquid to said wall portion is larger than that of saidfirst liquid to said 1^(st)-A electrode and said 1^(st)-B electrode. 5.The display system of claim 3, wherein there is a thin film provided onsaid second electrode that faces said liquid confining space, wherein awettability of said second liquid to said thin film is smaller than thatof said second liquid to said 1^(st)-A electrode and said 1^(st)-Belectrode.
 6. The display system of claim 3, wherein a lipophilicinsulating film is located over the surfaces of said 1^(st)-A electrodeand said 1^(st)-B electrode coming into contact with said first andsecond liquids.
 7. The display system of claim 6, wherein a wettabilityof said first liquid to said wall portion is larger than that of saidfirst liquid to said insulating layer.
 8. The display system of claim 6wherein there is a thin film provided on said second electrode thatfaces said liquid confining spaces wherein a wettability of said secondliquid to said thin film is smaller than that of said second liquid tosaid insulating layer.
 9. The display system of claim 3, wherein saidintermediate partition has a height enough to ensure that when theapplied voltage is shut off, said second liquid resting on said 1^(st)-Aelectrode or said 1^(st)-B electrode does not go over it.
 10. Thedisplay system of claim 2, characterized in that said assembly comprisesa set of substrates, at least one of which is transparent, a wallportion for holding said set of substrates in opposition to one anotherin such a way as to define a liquid confining space, a 1^(st)-Aelectrode and a 1^(st)-B electrode that are located on one substratethat faces said liquid confining space in an electrically independentway, an intermediate partition located at a boundary site between said1^(st)-A electrode and said 1^(st)-B electrodes to divide said liquidconfining space in a direction along said substrate surface, and asecond electrode that is located on another substrate that faces saidliquid confining space, wherein said 1^(st)-A electrode and said1^(st)-B electrode are electrically insulated from said first and secondliquids; said intermediate partition has an opening that defines aliquid flow path; at a voltage applied to said 1^(st)-A electrode andsaid second electrode or a voltage applied to said 1^(st)-B electrodeand said second electrode, said second liquid passes through the openingin said intermediate partition in such a way as to be able to migratebetween on said 1^(st)-A electrode and on said 1^(st)-B electrode; andsaid intermediate partition works as said liquid retainer means.
 11. Thedisplay system of claim 10, wherein a wettability of said first liquidto said wall portion is larger than that of said first liquid to said1^(st)-A electrode and said 1^(st)-B electrode.
 12. The display systemof claim 10 wherein there is a thin film provided on said secondelectrode that faces said liquid confining space, wherein a wettabilityof said second liquid to said thin film is smaller than that of saidsecond liquid to said 1^(st)-A electrode and said 1^(st)-B electrode.13. The display system of claim 10 wherein a lipophilic insulating filmis located over surfaces of said 1^(st)-A electrode and said 1^(st)-Belectrode coming into contact with said first and second liquids. 14.The display system of claim 13 wherein a wettability of said firstliquid to said wall portion is larger than that of said first liquid tosaid insulating layer.
 15. The display system of claim 13 wherein thereis a thin film provided on said second electrode that faces said liquidconfining space, wherein a wettability of said second liquid to saidthin film is smaller than that of said second liquid to said insulatinglayer.
 16. The display system of claim 10 wherein said second liquid hasa surface tension of 10 to 73 dyne/cm at 20° C., and said opening insaid intermediate partition has a width of 1 to 1,000 μm.
 17. Thedisplay system of claim 3 wherein a desired pattern of light block filmis provided externally of the transparent substrate on a display viewingside.
 18. The display system of claim 10 wherein a desired pattern oflight block film is provided externally of the transparent substrate ona display viewing side.
 19. The display system of claim 3, wherein saidsecond liquid is colored oil.
 20. The display system of claim 10,wherein said second liquid is colored oil.
 21. The display system ofclaim 19, wherein there is a reflection type display where lightreflected from within the display cell is viewed, and the colored oilthat is said second liquid filled in each display cell is any one ofyellow, magenta, and cyan.
 22. The display system of claim 20, whereinthere is a reflection type display where light reflected from within thedisplay cell is viewed, and the colored oil that is said second liquidfilled in each display cell is any one of yellow, magenta, and cyan. 23.The display system of claim 19, wherein there is a transmission typedisplay where light transmitting through the display cell is viewed, andsaid first liquid is colored water while the colored oil that is saidsecond liquid is a light blocking black oil.
 24. The display system ofclaim 20, wherein there is a transmission type display where lighttransmitting through the display cell is viewed, and said first liquidis colored water while the colored oil that is said second liquid is alight blocking black oil.
 25. The display system of claim 23, whereinthe colored water that is said first liquid filled in each display cellis any one of red, green, and blue.
 26. The display system of claim 24,wherein the colored water that is said first liquid filled in eachdisplay cell is any one of red, green, and blue.
 27. The display systemof claim 3, wherein said 1^(st)-A electrode and said 1^(st)-B electrodefor each display cell are identical in configuration and position. 28.The display system of claim 10, wherein said 1^(st)-A electrode and said1^(st)-B electrode for each display cell are identical in configurationand position.
 29. The display system of claim 2, wherein said assemblycomprises a set of substrates, at least one of which is transparent, awall portion for holding said set of substrates in opposition to oneanother in such a way as to define a liquid confining space, a 1^(st)-Aelectrode located on one substrate that faces said liquid confiningspace, a 1^(st)-B electrode located on another substrate that faces saidliquid confining space, and a second electrode located substantiallyparallel with said 1^(st)-A electrode and said 1^(st)-B electrode andadapted to divide said liquid confining space, wherein said secondelectrode has a plurality of through-holes in at least a part, said1^(st)-A electrode and said 1^(st)-B electrode are electricallyinsulated from said first and second liquids; at a voltage applied tosaid 1^(st)-A electrode and said second electrode or a voltage appliedto said 1^(st)-B electrode and said second electrode, said second liquidpasses through the through-holes in said second electrode in such a wayas to be able to migrate between said liquid confining space on said1^(st)-A electrode and said liquid confining space on said 1^(st)-Belectrode; and said second electrode works as said liquid retainermeans.
 30. The display system of claim 29, wherein said second electrodeis an electrically conducting material having a plurality ofthrough-holes.
 31. The display system of claim 29, wherein said secondelectrode is defined by an electrically conducting film formed on asurface of an insulating material having a plurality of through-holes.32. The display system of claim 29, wherein a wettability of said firstliquid to said wall portion is larger than that of said first liquid tosaid 1^(st)-A electrode and said 1^(st)-B electrode.
 33. The displaysystem of claim 29, wherein there is a thin film provided on said secondelectrode, wherein a wettability of said second liquid to said thin filmis smaller than that of said second liquid to said 1^(st)-A electrodeand said 1^(st)-B electrode.
 34. The display system of claim 29, whereina lipophilic insulating film is located over surfaces of said 1^(st)-Aelectrode and said 1^(st)-B electrode.
 35. The display system of claim34, wherein a wettability of said first liquid to said wall portion islarger than that of said first liquid to said insulating layer.
 36. Thedisplay system of claim 34, wherein there is a thin film provided onsaid second electrode, wherein a wettability of said second liquid tosaid thin film is smaller than that of said second liquid to saidinsulating layer.
 37. The display system of claim 29, wherein saidsecond liquid has a surface tension of 10 to 73 dyne/cm at 20° C., andsaid through-holes in said second electrode have a width of 1 to 1,000μm.
 38. The display system of claim 29, wherein a desired pattern oflight blocking film is provided externally of the transparent substrateon a display viewing side.
 39. The display system of claim 29, whereinsaid second liquid is colored oil.
 40. The display system of claim 39,wherein there is a reflection type display where light reflected fromwithin the display cell is viewed, and the colored oil that is saidsecond liquid filled in each display cell is any one of yellow, magenta,and cyan.
 41. The display system of claim 2, characterized in that saidassembly comprises a set of substrates, at least one of which istransparent, a wall portion for holding said set of substrates inopposition to one another in such a way as to define a liquid confiningspace, a 1^(st)-A electrode and a 1^(st)-B electrode that are located onone substrate that faces said liquid confining space in an electricallyindependent way, an oil repellent layer located at a boundary sitebetween said 1^(st)-A electrode and said 1^(st)-B electrode, alipophilic layer located in such a way as to cover said 1^(st)-Aelectrode and said 1^(st)-B electrode at a site with no said oilrepellent layer located, and a second electrode that is located onanother substrate that faces said liquid confining space, wherein said1^(st)-A electrode and said 1^(st)-B electrode are electricallyinsulated from said first and second liquids; and at a voltage appliedto said 1^(st)-A electrode and said second electrode or a voltageapplied to said 1^(st)-B electrode and said second electrode, saidsecond liquid goes over said oil repellent layer in such a way as to beable to migrate between on said 1^(st)-A electrode and on said 1^(st)-Belectrode; and said oil repellent layer works as said liquid retainermeans.
 42. The display system of claim 41 wherein said oil repellentlayer and said lipophilic layer are located over said 1^(st)-A electrodeand said 1^(st)-B electrode by way of an insulating layer.
 43. Thedisplay system of claim 41, wherein said oil repellent layer and saidlipophilic layer each possess electrical insulation.
 44. The displaysystem of claim 41, wherein said oil repellent layer is configured insuch a way as to project toward said liquid confining space.
 45. Thedisplay system of claim 41, wherein a wettability of said first liquidto said wall portion is larger than that of said first liquid to saidoil repellent layer and said lipophilic layer.
 46. The display system ofclaim 41, wherein there is a thin film provided on said second electrodethat faces said liquid confining space, wherein a wettability of saidsecond liquid to said thin film is smaller than that of said secondliquid to said oil repellent layer and said lipophilic layer.
 47. Thedisplay system of claim 41, wherein a desired pattern of light blockfilm is provided externally of the transparent substrate on a displayviewing side.
 48. The display system of claim 41, wherein said secondliquid is colored oil.
 49. The display system of claim 48, wherein thereis a reflection type display where light reflected from within thedisplay cell is viewed, and the colored oil that is said second liquidfilled in each display cell is any one of yellow, magenta, and cyan. 50.The display system of claim 48, wherein there is a transmission typedisplay where light transmitting through the display cell is viewed, andsaid first liquid is colored water while the colored oil that is saidsecond liquid is a light blocking black oil.
 51. The display system ofclaim 50, wherein the colored water that is said first liquid filled ineach display cell is any one of red, green, and blue.
 52. The displaysystem of claim 41, wherein said 1^(st)-A electrode and said 1^(st)-Belectrode for each display cell are identical in configuration andposition.
 53. A manufacture method for manufacturing the display systemof claim 41, characterized in that: an oil repellent resin layer isformed, and said resin layer is subjected to pattern exposure to make anexposed site lipophilic, thereby forming said oil repellent layer andsaid lipophilic layer.
 54. The manufacture method of claim 53, whereinsaid oil repellent resin layer is subjected to pattern exposure by wayof a photocatalyst layer.
 55. A display medium comprising at least onedisplay system as recited in claim 1, characterized by comprising: aninput terminal for feeding power and signals from external equipment toeach display cell in said display system, wherein at said input terminalsaid display medium can be connected to or disconnected from saidexternal equipment.
 56. A display medium comprising at least one displaysystem as recited in claim 2, characterized by comprising: an inputterminal for feeding power and signals from external equipment to eachdisplay cell in said display system, wherein at said input terminal saiddisplay medium can be connected to or disconnected from said externalequipment.
 57. A display medium comprising at least one display systemas recited in claim 3, characterized by comprising: an input terminalfor feeding power and signals from external equipment to each displaycell in said display system, wherein at said input terminal said displaymedium can be connected to or disconnected from said external equipment.58. A display medium comprising at least one display system as recitedin claim 10, characterized by comprising: an input terminal for feedingpower and signals from external equipment to each display cell in saiddisplay system, wherein at said input terminal said display medium canbe connected to or disconnected from said external equipment.
 59. Adisplay medium comprising at least one display system as recited inclaim 29, characterized by comprising: an input terminal for feedingpower and signals from external equipment to each display cell in saiddisplay system, wherein at said input terminal said display medium canbe connected to or disconnected from said external equipment.
 60. Adisplay medium comprising at least one display system as recited inclaim 41, characterized by comprising: an input terminal for feedingpower and signals from external equipment to each display cell in saiddisplay system, wherein at said input terminal said display medium canbe connected to or disconnected from said external equipment.